With the development of data storage techniques, various data storage devices now provide users with higher data storage capacity, and also their speed of accessing data has been increased greatly. Besides the increase of data storage capacity, users also impose greater and greater demands on data reliability and response time of storage systems. So far various RAID-based data storage systems have been developed to increase data reliability. When one or more disks in a storage system fail, data in failing disks can be recovered from data in other disks operating normally.
The storage system may be accessed via storage control nodes. In a typical active-active type of storage system, two storage node controls work jointly to process data access operations on the storage system and further provide higher availability and better performance. Each storage control node has its own memory (e.g. cache), and memories in two storage controllers operate in a mirroring mode. The two storage control nodes may concurrently receive data access instructions from the outside. At this point, it becomes a focus of research regarding how to ensure the scheduling of available storage spaces of memories in the two storage control nodes.